1. Field of the Invention
The present invention relates to a diagnosis apparatus and method and, more particularly, to a diagnosis apparatus connected to a communication bus of a time-division multiplex (TDM) communication system to diagnose the communication system from a communication signal flowing through the communication bus.
2. Background Information
Conventional TDM communication system are known including event trigger communication systems and time trigger communication systems as described for example, in JP2006-319394A.
The event trigger communication system is so constructed that transmission object data is transmitted and received between nodes only when each node outputs a communication demand or request along with occurrence of an event enabling the node to acquire the right to transmit.
The time trigger communication system is so constructed that a certain time interval associated with a communication cycle is divided into a plurality of time slots. Non-overlapping individual time slots are assigned to respective nodes and each node transmits data in the assigned individual time slot.
In order to manage the time trigger communication system, it is necessary to set a communication schedule to each node through various communication parameters such as the number of time slots, a bit length, a slot length and a frame length. These communication parameters are required to be determined in consideration of factors such as a clock precision and a communication bus delay. Therefore, in the time trigger-type communication system when suitable factors are not sufficient or are not present, there can be cases where the communication system can not operate in accordance with design parameters.
Further, since data transmission timing from each node is defined by the time slot in the time trigger communication system, when generation of the transmission object data is not completed in time for transmission in the proper slot associated with the transmission timing due, for example, to execution delay of an application program, the transmission object data can not be transmitted from the associated node, creating a state where the node is free from transmitting the data.
As described above, there can be cases where the time trigger communication system does not normally operate due to various causes. Therefore, conventionally, a diagnosis apparatus can be used to determine whether communication in the communication system is properly carried out.
Conventional diagnosis methods are also known for diagnosing a time trigger communication system where, for example, a communication signal from the communication system is decoded and then recorded. A designer then analyzes the recorded content with a computer for diagnosis. In another conventional diagnosis method, a diagnosis apparatus is arranged to be operated in synchronization with a time trigger communication system by setting a communication schedule in coordination with the diagnosis apparatus and diagnosing the time trigger communication system from the synchronized state.
The conventional diagnosis methods, however, have the following disadvantages. For example, in the method of diagnosing the communication system where the communication signal is decoded and then recorded and a designer analyzes the recorded content with a computer for diagnosis, the content of the communication signal can be recognized as codes of “0” and “1”, but potentially abnormal time-based behavior associated with the transmission action of the frame can not be recognized. Accordingly, the communication system can not be diagnosed in real time.
In the method of making the diagnosis apparatus operate in synchronization with the communication system, when an erroneous communication parameter is set in the diagnosis apparatus, based on synchronized operation, an appropriate diagnosis can not be carried out. In addition, since the setting error of the communication parameter is difficult to be recognized, a designer or troubleshooter may spend time for wasteful consideration attempting to solve the communication system failure.
A technology for automatically setting the communication schedule to the diagnosis apparatus is described in JP2006-319394A. However, with regard the subject technology of JP2006-319394A when diagnosis of another communication system in addition to the time trigger communication system is desired, the diagnosis apparatus is arranged to be operated to be synchronized with the communication system by acquiring the communication schedule from a gateway unit connecting these networks. Therefore, such a method can not be used other than in an environment where the different communication systems are provided together.